The present invention relates to an internet-work apparatus for connecting a plurality of networks at a network layer level, and more particularly to techniques effective for application to an internetwork apparatus which continues an operation of connecting a plurality of networks by performing a degeneration process when a fault occurs.
In a system in which one internetwork apparatus connects a plurality of networks, if a fault occurs in the internetwork apparatus, a protocol process between networks becomes impossible so that communication between networks stops and the operation of the whole system may stop.
In such a case, if two internetwork apparatuses are used for configuring a redundancy system and the current system and standby system of the internet-work apparatuses are switched, a high reliability system can be provided.
As techniques of running a system by switching between two internetwork apparatuses, there is known as disclosed, for example, in JP-A-3-78339, a redundancy system in which when a fault occurs in the current system, the whole system is switched to the standby system.
Since the conventional redundancy system uses two current and standby internetwork apparatuses, it becomes necessary to add a standby internetwork apparatus to a current internetwork apparatus so that the system cost becomes high.
It is an object of the present invention to solve the above problem and provide techniques capable of performing routing even when a fault occurs in a route calculating module without adding a new system.
It is another object of the present invention to provide techniques capable of reducing a process load of a management module which substitutes for the function of a route calculating module.
According to the present invention, in an internetwork apparatus interconnecting a plurality of networks, a management module performs routing by substituting for the function of a route calculating module when a fault occurs in the route calculating module.
During a normal operation of the internetwork apparatus of this invention, the route calculating module forms a first routing table through the operation of a first routing protocol process unit. In accordance with the first routing table of the route calculating module, a repeating process or relay module determines a repeating destination of each packet.
A fault detecting process unit of the management module enquires the operation state of the route calculating module and checks its response to judge whether any fault occurs in the route calculating module.
When a fault is detected in the route calculating module, the management module activates a second routing protocol process unit of the management module and forms a second routing table of the management module through the operation of the second routing protocol process unit.
Next, a routing table reference destination change notice process unit notifies the repeating process module of a routing table reference destination change notice which indicates that the routing table to be referred to by the repeating process module when the repeating process module repeats a packet, was changed from the first routing table of the route calculating module to the second routing table of the management module.
A routing table reference destination change notice reception unit of the repeating process module receives the routing table reference destination change notice notified by the management module, and changes the routing table to be referred to by the repeating process module when the repeating process module repeats a packet, from the first routing table of the route calculating module to the second routing table of the management module. In accordance with the second routing table of the management module, the repeating process module determines a repeating destination of each packet and transmits the packet.
The cost of a high reliability redundancy system using a plurality of internetwork apparatuses is high. However, the internetwork apparatus of this invention described above can realize a high reliability system at a low cost because the management module substitutes for the function of the route calculating module.
As above, according to the internetwork apparatus of this invention, since the management module substitutes for the function of the route calculating module when a fault occurs in the route calculating module, it is possible to perform routing even if a fault occurs in the route calculating module, without adding a new system.
Further, according to an embodiment of the internetwork apparatus, since the contents of a substitute process to be executed by the management module when a fault occurs in the route calculating module, are limited, the process load of the management module which substitutes for the function of the route calculating module can be reduced.